What I meant by open world VN is like the immensely popular Lustful Desires game or even Hornstown - basically games that let you explore areas on a custom map. Beast Control (which the deepest level I got to was 17 and I absolutely love the Oni image) reminds me a lot of Grove (another incredibly popular and wonderful game with Open World elements).
Between the Beast Control style game and the Cumdy Werewolf (and other creatures) and even the Grinding Club, I think you could make a (extremely ambitious) great open world style VN out of it. :D Just food for thought. ;)